warden: Use ext2 for ephemeral volumes
warden: Use ext2 for ephemeral volumes

There's no need for journaling and ext2 is faster.

Change-Id: Ife96d3a29eebee0cad73f09180fc56169550a20d

shashidharatd/garden-linux,shashidharatd/garden-linux,cloudfoundry-incubator/garden,tsaleh/garden,shashidharatd/garden-linux,tangfeixiong/garden,cloudfoundry-incubator/garden-linux,savaki/garden,cloudfoundry-incubator/garden-linux,savaki/garden,tangfeixiong/garden,shashidharatd/garden-linux,cloudfoundry-incubator/garden,tsaleh/garden,cloudfoundry-incubator/garden-linux